The present invention relates generally to the treatment and monitoring of industrial systems and, more specifically, to the treatment and monitoring of industrial systems using luminol-tagged polymers in combination with fluorescent or chemiluminescent detection techniques.
The ability to track the polymer location and concentration in industrial systems is highly desirable. Typically, these processes are complex and dynamic, and therefore the means to monitor the polymeric coagulant or flocculent can result in increases in efficiency of the chemical treatment program, allow for diagnostic troubleshooting, insure that regulatory discharge limits are met, and may allow for automated control of the polymer treatment program by relating the monitoring parameter to some other system parameter of interest, for example, drainage rate or turbidity reduction. The industries in which such water soluble polymers are used include papermaking, mining and mineral process, sludge dewatering, and oil recovery, for example. Water soluble polymers of the type described herein are also used extensively to treat water used for steam generation (boilers) and cooling, among other things.
The typical approach to monitoring the level of water soluble polymer coagulants or flocculants in a system has been to blend fluorescent dyes with the polymer program in small amounts and to use the fluorescence of the mixture to determine the concentration of the polymer in the system, as exemplified by U.S. Pat. Nos. 4,783,314; 5,645,799 and 5,435,969, the disclosures of which are hereby incorporated by reference.
Another approach involves the preparation of "tagged" polymers, wherein a fluorescent moiety is covalently attached to the polymer, either during or after the polymerization, and then utilized for fluorescence monitoring and dosage control. This approach is described in U.S. Pat. Nos. 4,813,973, 5,171,450 and 5,705,394, the disclosures of which are also hereby incorporated by reference. Fluorescent compounds incorporated into monomers have also been disclosed in GB 1,141,147. This approach is advantageous in that the detection of flourescence positively indicates the presence of the polymeric additive. While both approaches for monitoring fluorescence have been relatively successful, they have limitations. Many aqueous systems wherein water soluble polymers are utilized often contain other sources of fluorescence. Therefore, the use of a fluorescent marker may be impractical, as it becomes difficult to reliably distinguish low levels of fluorescence from the polymeric species against high levels of fluorescence arising from the process stream or waste water. Moreover, such process waters oftentimes contain substances which may not be fluorescent themselves, but which will quench the fluorescence of other species in the system, including the fluorescence of the traced or tagged polymer additive. This also makes reliable detection of the polymer additive difficult or impossible. Finally, if the levels of the background fluorescence or the quenching materials fluctuate, this renders useless automated control schemes based on the calibration of a fluorescent response.
Accordingly, there is a need for a polymer that can be modified with a marker chemically incorporated into or otherwise attached to the polymer. Because the marker and polymer would be physically attached, detection of the marker would necessarily result in a detection of the polymer. Of course, it would be economically important that the marker be readily detectable at low concentrations. A chemiluminescent marker would therefore be desirable, since chemiluminescence is based upon a non-irradiative excitation process, and therefore is not subject to the same limitations of fluorescence-based monitoring techniques already discussed. Further, for widespread applicability, a water soluble polymer is required. Accordingly, there is a need for a modified water soluble polymer in which the marker is highly chemiluminescent and which could be readily detected in the part per million (ppm) or part per billion (ppb) range using existing chemiluminescent techniques.
Luminescent labels are attractive candidates for use as markers for a variety of reasons. Chemiluminescence is broadly defined as the production of visible light by atoms that have been excited by the energy produced in a chemical reaction, usually without an associated production of heat. Chemical energy excites electrons in the light-emitting molecules to higher energy states, from which electrons eventually fall to lower energy states with the emission of quanta of energy in the form of visible light. Luminescence is observed in several synthetic chemical compounds and also in naturally occurring biological compounds such as found in some bacteria, fireflies and certain varieties of marine life.
One of the most important families of chemiluminescent molecules are the phthalhydrazides. The most familiar member of this family is luminol, or 5-amino-2,3-dihydro-1,4-phthalazinedione, which has a chemical composition of C.sub.8 H.sub.7 N.sub.3 O.sub.2 and a double ring structure with a melting point of about 320.degree. C. Luminol is commercially available from several suppliers and is well characterized. Certain luminol analogs are also chemiluminescent, such as those wherein the position of the amino group is shifted (e.g., isoluminol, the amino group being at the 6 position), or is replaced by other substituents, as well as annelated derivatives and those with substitution in the non-heterocyclic ring. Some luminol analogs produce light more efficiently than does luminol itself, while others have lower efficiency. (As used herein, the term "luminol" encompasses such related species.)
Generally, luminol produces light in an oxidizing reaction, wherein the luminol combines with oxygen or an oxidizer to produce a reaction product and photons at a wavelength of about 425-450 nanometers (nm). The precise reaction formula and the quantum efficiency of light production, i.e., the ratio of luminescing molecules to total molecules of the luminescent species, depend upon the medium in which the luminol resides, temperature and other reaction conditions. Typical oxidizers used in conjunction with luminol include oxygen, hydrogen peroxide, hypochlorite, iodine and permanganate.
The oxidation of luminol with the associated production of light occurs rather slowly at ambient temperatures, unless the reaction is catalyzed. A variety of different substances can catalyze the reaction, including organic enzymes, such as horseradish peroxidase, other organic molecules such as microperoxidase and heme, positively charged metallic ions such as the cupric ion, and negatively charged ions such as the ferricyanate ion among others.
Luminol has been diazo-linked to hydroxyindole to form water-soluble luminescent compounds having repeating units, for use in immunoassays as described in U.S. Pat. No. 5,003,050. Moreover, post-polymerization modification of water-soluble polymers with luminol to produce filling agents or immunologically active complexes for quantitative assays was disclosed in JP 58137759A and JP 05034330. However, therein structurally different polymers were first formed, and luminol was afterwards attached, in contrast to the instant invention wherein luminol is incorporated into a monomer prior to polymerization.
Luminescent molecules would appear to be highly desirable as markers because of their stability, sensitivity, the potential ease of detecting their emitted visible light and their lack of toxicity.
There is a need for a luminescent water treatment agent which is water soluble, is highly quantum efficient, and provides long-lived chemiluminescence. Accordingly, it is an object of the present invention to provide a water-soluble luminescent water treatment agent. The inventors have discovered that use of a luminol derived marker, incorporated into a polymeric water treatment agent by free radical polymerization of luminol derived monomers achieves such goals. The novel chemiluminescent polymers will have utility for polymer detection, product fate determination and dosage control. Moreover, since emission is chemically induced, no photo excitation source is used, and fluorescence resulting from other components or contaminants of the system to be treated will not interfere with quantitation. Moreover, since chemiluminescence may be detected at very low levels, the tagged polymers disclosed herein provide the additional advantage of more exact quantitation.
Other objects, aspects and advantages of the present invention will be apparent to those skilled in the art from a reading of the following detailed disclosure of the invention.